Nanoimprint lithography is quickly gaining ground as a cost-effective substitute for optical lithography as feature sizes across the electronics industries continue to shrink.
The hard disk drive manufacturing industry is becoming an early adopter of nanoimprint technology. The need to continually increase disk media areal densities has led to the development of Discrete Track Recording (DTR) media and Bit Patterned Media (BPM), typically consisting of concentric lines and grooves in the case of DTR, and 2-dimensional grids of holes in the case of BPM. Roadmap goals for DTR and BPM structures are 20 nm and 25 nm half pitch, respectively, to be achieved in progressive steps between now and 2015 (“From Possible to Practical—The Evolution of Nanoimprint Lithography for Patterned Media”, P. Hofemann, Session 6, Diskcon Asia-Pacific (2009)).
Examples of attempts to apply conventional scatterometry and/or optical critical dimension (OCD) solutions to nanoimprint lithography in the prior art focus mainly on larger feature sizes, and ignore—or simply brush off without further comment—the trends of disk media roadmaps that will eventually result in much smaller feature sizes. Examples include “Characterizing Nanoimprint Profile Shape and Polymer Flow Behavior using Visible Light Angular Scatterometry”, R. Alassaad, L. Tao, S. W. Pang, and W. Hu, Nano Lett. Vol 6. No. 8, pp. 1723-1728 (2006); “Scatterometry for in situ measurement of pattern reflow in nanoimprinted polymers”, H. J. Patrick, T. A. Germer, Y. Ding, H. W. Ro, L. J. Richter, and C. L. Soles, Appl. Phys. Lett, Vol. 93, 233105 (2008); and “Fully Automated Non-Destructive Metrology for Imprint Templates, DTR, and BPM Media”, I. Bloomer, Session 7, Diskcon Asia-Pacific (2009).